The immediate objective of this investigation is to perfect methods to measure noninvasively in humans the amount of lung tissue in contact with the airways, and pulmonary capillary blood flow (Qc) by rebreathing insoluble and soluble gases. Studies in normal humans will determine the optimum breathing rate, lung volume, depth of breathing, and body position that gives the most reproducible results. Various methods of timing, sampling, and ventilating the initial dead space will be explored and normal values collected. Using the best method developed patients with chronic pulmonary edema and pulmonary fibrosis will be studied. Accuracy of tissue volume measurements will be assessed by comparison to lung weights measured by a method using computerized tomography (CT). Accuracy of Qc will be determined by comparisons to indicator dilution measurements of cardiac output. In normal dogs and dogs in pulmonary edema, the CT method of measuring lung weight will be compared to postmortem lung weights to determine if CT lung weights are accurate. Bleomycin-induced pulmonary fibrosis will be evaluated in additional dogs while monitoring tissue volume, CT weight, lung recoil, transbronchial biopsies, lung lavage fluid, and chest x-rays to determine the most sensitive detector of developing pulmonary fibrosis. In a dog model of high permeability pulmonary edema produced by air emboli, microscopic alterations and sites of vascular leakage will be documented. Experiments that vary pulmonary pressure, loci of emboli, blood constituents, pharmacological blocking agents will be performed and correlated with microscopic pathology in order to uncover mechanisms producing edema. In order to develop a method that can detect increased lung permeability prior to pulmonary edema, we will study rate of clearance in dogs of monodispersed radioactive aerosols of different sizes containing substances with different molecular weights, solubilities, and structures. Clearance rates will be appraised by scintillation cameras and arrival of indicators in the peripheral blood.